1) Retroviruses that express viral and common tumor antigens prevented 3-MC cancers in mice and rats. 2) Retroviral immunotherapy of cancer(s) in dogs provided 8 long-term remissions and several possible cures. 3) Five retroviruses, concentrated 1000X, were safety tested in chimpanzees and demonstrated to be innocuous, thus suggesting the possibility for their use in humans immunotherapeutically. 4) Lymphoma epidemics in hamsters were traced to an ambient "viroid" present in contaminated rooms in studies at several laboratory sites (Drs. Huebner, Coggin and Gilden). 5) Retroviral therapy of carcinogen-induced liver tumor in primates has not been successful. However, immunoprevention experiments to suppress carcinogen-induced primate cancer appear feasible. 6) Skin transformation assays to identify individuals of cancer syndrome families at high risk for cancer was 80% successful in one test, 100% in the second. Forty specimens are now being run blindly in 3 laboratories for confirmation of results.